LeetCode: Largest Rectangle in Histogram

LeetCode: Largest Rectangle in Histogram

Given n non-negative integers representing the histogram’s bar height where the width of each bar is 1, find the area of largest rectangle in the histogram.


Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3].


The largest rectangle is shown in the shaded area, which has area = 10 unit.

For example,
Given height = [2,1,5,6,2,3], return 10.

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public class LargestRectangleInHistogram {

    public int largestRectangleArea(int[] height) {
        if (height == null || height.length == 0) {
            return 0;
        }
        Stack<Integer> stack = new Stack<Integer>();
        int[] arr = Arrays.copyOf(height, height.length + 1);

        int crt = 0;
        int max = 0;
        while (crt < arr.length) {
            if (stack.isEmpty() || arr[crt] >= arr[stack.peek()]) {
                stack.push(crt++);
            } else {
                int i = stack.pop();
                max = Math.max(max, arr[i] * (stack.isEmpty() ? crt : crt - stack.peek() - 1));
            }
        }

        return max;
    }
}